PROJECT SUMMARY/ABSTRACT Systemic lupus erythematosus (SLE) predominantly affects women, up to ten times more frequently than men, and it occurs about five times more commonly in African Americans than in Caucasians. Although the primary cause of SLE has not yet been identified, a combination of genetic, hormonal, and environmental factors is known to contribute to the development of this disease. Studies during recent years suggest that the disease process initiates in genetically susceptible subjects several years before the development of clinical disease and it could be suppressed or accelerated by sex hormones and environmental factors including gut microbiota. This suggests that increased understanding of the environmental and genetic factor interactions that trigger/perpetuate the early events of disease processes and identification of early predictors of autoimmune processes will help develop novel safe and effective strategies to control or prevent SLE, prior to the onset of clinical disease. In this regard, using a pre-clinical model of lupus which shares the etiology and auto-antigen epitopes with that of human SLE, we for the first time, demonstrate the contribution of pro-inflammatory events and autoantibody production initiated in the gut mucosa at juvenile age, long before the onset of systemic autoimmunity and clinical disease, in the onset of disease process. We have also identified a combination of previously unknown molecular events that initiates gut-inflammation and autoantibody production in a TLR7/8- gut microbiota interaction-dependent manner, and contributes to systemic autoimmunity and lupus disease progression. Based on our preliminary observations, we hypothesize that ?the systemic autoimmune process in lupus is initiated and perpetuated by TLR7/8-gut microbiota interaction dependent inflammation and autoantibody production in the gut mucosa, and inhibition of this interaction at pre-nephritis stages can effectively prevent the disease in at-risk subjects, and suppress autoantibody production in lupus patients?. Here, we propose studies: 1) to define the role of TLR7/8 -microbiota interaction dose in human SLE by associating gut inflammation and permeability features with the expression levels of these receptors on immune cells, and microbiota interaction-dependent pro-inflammatory responses of these cells, with autoimmunity and lupus susceptibility; and 2) to elucidate the role of TLR7/8-gut microbiota interaction in initiating gut inflammation and autoantibody production, and systemic autoimmunity using pre-clinical models. We will also determine the potential of oral treatment with antagonists in preventing/suppressing gut inflammation, systemic autoimmunity and disease incidence. Our proposed study will not only identify early pro-inflammatory events that initiate systemic autoimmunity in lupus, but will also introduce the possibility of a novel and rational, oral therapy for suppressing intestinal inflammation to prevent SLE in at-risk subjects and flares in subjects with established SLE.